From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Article from 'The Autocar' magazine discussing car body design, weight distribution, and frame distortion.
| Identifier | ExFiles\Box 160\2\ scan0003 | |
| Date | 8th August 1914 | |
| 264 THE AUTOCAR, August 8th, 1914. Considerations of Body Design. upon the tyres, but also upon the steering mechanism, radius rods, and springs. It may incidentally be pointed out that there are other ways in which the chassis designer betrays his ignorance of the importance of moments of inertia, no less than the body maker, for the former in the modern car nearly always insists in putting a huge petrol tank at the extreme rear of the car, the weight of the contents being comparable with that of a fair-sized human being, whilst the only position in which it would seem that luggage can be carried on the average body is at a point even further back. Spare tyres, rims, and wheels are often found as additional tail appendages, and taking all these facts into consideration, it is really not at all surprising that one hears complaints about springing and the difficulties of making cars hold the road. As an illustration which conclusively shows that people do realise the effect, even if they do not appreciate the cause, I may mention that I recently completed a little over nine thousand miles on a set of five Victor tyres fitted to a two-seated 15-20 h.p. Métallurgique. Everybody who has been told of this performance has admitted that it was a remarkable one, and an extraordinary testimony to good tyre construction, but many have not failed to remark that "after all, you know, it's a two-seater, and that makes a lot of difference, because it is, of course, much lighter than a four-seater of the ordinary type." Now, as a matter of fact, it is nothing of the kind, because it is really a rather clumsily built two-seater, and a test on a weighbridge has shown that it is appreciably heavier than the four-seater body generally fitted to the same chassis. I believe it is undeniable that, apart from the excellence of the tyres themselves, and three of them, like the man in the whisky advertisement, are “still going strong,” part of the credit at least rests with the fact that the distribution of weight has not been so grossly subversive of all mechanical principles as it is in the ordinary body. Truly the tyre-making industry is making great strides forward in its progress towards perfection, when it, in several instances, can guarantee a minimum mileage, in spite of the fact that chassis constructors and body builders are doing their very worst in attacking the car on its weakest side. Some indignant voice will no doubt say that this is not the body maker's concern at all, and that it is his business simply and solely to make something which will seat his passengers comfortably. In that case I consider him to have little title to the name of designer, for I submit that if the word “design” means anything at all, it means that everything, even remotely connected with the end in view, is taken into consideration. At risk of being accused of labouring the point, or rather points, I would merely add before proceeding to another phase of the subject altogether, that, although there are difficulties inseparable from every new type of construction which will naturally crop up when some body builder has the courage to build his carriage work on rational lines, these difficulties can be overcome, even though at first sight they may appear insuperable. The worst of these is that the chassis maker and the body maker seem to have no common cause, if anything they work against, rather than with one another, and if you want to hear a poor opinion of the former, go to the workshops of the latter, and vice versa. It is always the other man's fault, and I am very much afraid that before anything can be done to improve cars in regard to the points which I have already dealt with, some courageous person will have to be found, who will go from the one to the other, and persuade the chassis manufacturer that the body builder has got his work to do besides himself, and represent to the latter that the former has got his demands under consideration. Things are at present none too hopeful, because one turns out a bad thing which the other makes worse. 3.—Frame Distortion. The other phase of the matter to which I have referred relates to a particular case of the old scientific chestnut, about an irresistible force meeting an immovable body. Making due allowance for boiling theory down into practice, this is the sort of thing that occurs when the very strong framework of a very strong body is mounted on the very strong framework of a very strong car. It is all very well for constructors of pressed steel frames to claim that their products are almost perfectly rigid, but the fact is, that when it comes to carrying heavy weights over rough roads at high speeds, distortion does occur to a very large extent. Fig. 7. Five-seater in elevation, with air currents. It would be interesting to know how many body builders have realised the fact that the framework upon which they mount their bodies is, on the road, not so perfectly rigid as it seems to be in the workshop. If they had any glimmering of the truth they would surely never attempt to fasten the two together by some inelastic connection, such as is constituted by the ordinary coach bolt. One or two firms have not been entirely hopeless in this respect, and thus on some bodies one will find a layer of insulating material of tolerable elasticity inserted between the body framework and the chassis members, whilst in another case the rigid dashboard is not made to form a permanent foundation for the scuttle. This is right enough as far as it goes, but it does not go far enough. To begin with, the strength of the body construction is not sufficient to rigidify the chassis members to any appreciable extent, and because it is the weaker of the two constructions, the body suffers most when the pinch comes. The result is rattle, looseness, and gaping cracks, all of which are, in the circumstances, to be expected. If the bodywork is to be made rigid—and its very form of construction with closely fitting doors and windows, and steel or other metal panels laid on a foundation of a wood framing, insists that it should be—it must necessarily be suspended as a separate unit from the chassis, even though the suspension should have an elastic range to a slight extent. Some adequate means of insulation must, however, be introduced, unless there is to be a battle for the mastery between mere woodwork and pressed steel, the result of which is inevitable. The amount of movement to be allowed for is comparatively slight, and many difficulties which would otherwise crop up are therefore absent. A sufficiently thick layer of rubber might answer the purpose very well, but it would be prohibitively expensive, and incapable of resisting time, light, and weather, unless | ||